Modern petroleum drilling and production operations demand a great quantity of information relating to the parameters and conditions downhole. Such information typically includes the location and orientation of the wellbore and drilling assembly, earth formation properties and drilling environment parameters downhole. The collection of information relating to formation properties and conditions downhole is commonly referred to as logging. For example, a well can be logged after it has been drilled, such as by using wireline systems and methods. A well can also be logged during the drilling process, such as by using measurement while drilling (MWD) and logging while drilling (LWD) systems and methods.
Various measurement tools may be used during a logging operation. One such tool is the resistivity tool, which includes one or more antennas for transmitting an electromagnetic signal into the formation and one or more antennas for receiving a formation response. When operated at low frequencies, the resistivity tool may be called an induction tool and at high frequencies, it may be called an electromagnetic wave propagation tool. Though the physical phenomena that dominate the measurement may vary with frequency, the operating principles for the tool are consistent. In some cases, the amplitude and/or the phase of the receive signals are compared to the amplitude and/or phase of the transmit signals to measure the formation resistivity. In other cases, the amplitude and/or phase of the receive signals are compared to each other to measure the formation resistivity.